Rudolph Clausius: one of Bonn’s greatest scientists. When did you start thinking about a commemorative event?
Vöhringer: When I came to the University of Bonn in 2004, students in an introductory lecture asked about my approach to teaching entropy. I started thinking then for the first time about how it all goes back to Clausius, who taught and researched in Bonn.
Meschede: Peter Vöhringer gets a lot of the credit as well for this commemorative year, who noted that his 200th birthday was coming up and insisted that we have to do something special. So we really threw ourselves into the project.
One of his prime achievements was inventing the concept of entropy. What’s the best way to explain to the layman the full importance of that?
Vöhringer: Entropy is a key concept of chemistry for knowing whether a process is subject to randomness and uncertainty. All variables typically used in chemistry experiments to indicate in what direction a process spontaneously proceeds derive from the concept of entropy, including Gibbs energy and Helmholtz energy. A cup falling off a table and breaking is an example of a spontaneous process. The reverse of this process is not observable. Entropy is useful for describing this reality.
Meschede: Clausius, who was an incredibly strong mathematician, noticed that process heat was the one quantity in the theory behind steam engines that was not mathematically well-defined. He observed and comprehended these processes with such clarity that he was able to formulate them in mathematical terms. And he utilized microscopic models, which today we would call atomic, to explain macroscopic phenomena like diffusion, thereby laying the foundations for modern statistical physics.
Such dedication to scientific inquiry ...
Meschede: He certainly was highly distinguishing and meticulate. And we were wondering how Clausius could have ended up in relative obscurity compared to other great scientists of that age. One reason no doubt is that the concept of entropy has never been easy for people to grasp generally. His talent in mathematics and abstract thinking were impressive, compared even to Helmholtz.
Did you find anything surprising in researching Clausius?
Vöhringer: One thing was that while primarily considered a physicist today, he was actually more precisely involved in chemistry. One of his close colleagues for example was Friedrich August Kekulé, with whom he maintained considerable dialogue, as well as mathematician Rudolf Lipschitz, also of Bonn. I was quite surprised at this collaborative aspect in his work, and to realize what standing he had among scientists in related fields.
So his work style was very much ‘interdisciplinary’?
Vöhringer: It certainly was. But what’s more, he was able to foresee even back then future societal impacts from such practices as burning coal, perceiving how advancements in the natural sciences give rise to questions of ethical responsibility. I believe his approach back then was wholly aligned with the spirit that informs our six Transdisciplinary Research Areas. In particular, the Transdisciplinary Research Area 'Matter' has brought the topic of entropy back into focus in the anniversary year, among other things with the lecture series 'The Moving Power of Heat'.
In a speech once he talked about how natural energy resources are limited, and about the responsibility we have toward future generations. That’s entirely contemporary, wouldn’t you say?
Meschede: Indeed, I find Clausius’ mental acuity so impressive that he was able to reach the general realization nearly 140 years ago that we have to limit ourselves to what the sun provides to live in balance on earth. I find his vision fascinating; to be able to look at the situation and see there is something there we will have to address.
Vöhringer: Already back then he was talking about sustainable methods for generating energy, and was probably thinking about hydroelectric power when he spoke of our lovely landscapes that will have to be altered to this end.
Yet many have never heard of him. Why is that?
Vöhringer: Clausius’ thermodynamics today is essentially considered a field of settled theory. Few areas of scientific inquiry are understood with such thoroughness, which no doubt is partly to his credit. [PA1] When he died, in 1888, physics was slowly evolving in the direction of quantum mechanics. Thereafter the [PA2] field developed at a torrid pace, giving rise to new experimental and theoretical tools useful for explaining natural phenomena. He was simply born too soon to be a part of the latter era, and his accomplishments came to be overshadowed in the nascent age of modern physics.
Meschede: I believe Clausius is deserving of a place alongside Helmholtz, among other scientific contemporaries, for the impact of his work is of a similar magnitude. His field of inquiry is highly abstract however; it is a pity that his life has been the subject of so very little research—his time in Bonn in particular.
That will surely be changing however, in part through renaming of the Institute for Physical and Theoretical Chemistry to the “Clausius Institute”, will it not?
Vöhringer: Certainly, naming such an institute after Clausius directs a focus on the content of his scientific career in relation to the kind of research being conducted there. Attaching his name to an institute entails great responsibility furthermore for future generations working at the institute, in view of the call to action voiced for example in his academic speech on limited natural resources.
